SALEM, Va. — With an eye on the Supreme Court ruling this week, Mitt Romney on Tuesday said President Barack Obama's time in office would have been wasted if the high court strikes down the president's signature health care overhaul.

The presumptive Republican presidential nominee previewed his health care strategy while speaking to supporters outside a Virginia machine manufacturer just two days before the Supreme Court was expected to rule on the constitutionality of Obama's signature domestic achievement.

"If Obamacare is not deemed constitutional, then the first three-and-a-half years of this president's term will have been wasted on something that has not helped the American people," Romney told more than 1,000 supporters gathered outside Carter Machinery in southwest Virginia. "If it is deemed to stand, then I'll tell you one thing, we're going to have to have a president – and I'm that one – that's going to get rid of Obamacare. We're going to stop it on day one."

At a fundraiser in Atlanta Tuesday, Obama countered that his health care law was critical to expanding health care coverage for millions of Americans and preventing companies from discriminating against people who are sick.

"We don't need to refight this battle over health care. It's the right thing to do," Obama said.

Romney's plan would not prevent health care companies from denying coverage to new customers with medical conditions. Nor would he force them to cover young adults on their parents' plans through age 26.

Though the economy remains the No. 1 worry for voters, the health care ruling could have the biggest near-term political impact. If the Supreme Court upholds the law, it would mean validation for the president and the Democrats in Congress responsible for its passage in 2010. But the overhaul mobilized small-government advocates and was a big force behind the GOP takeover of the House that year. So if the law is upheld, Republicans have a clear case to make for strengthening their numbers and their power to overturn all or parts of it.

Romney has public events scheduled Tuesday and Wednesday in Virginia, a state that has been an aggressive opponent to the health care law under Attorney General Ken Cuccinelli. The former Massachusetts governor is expected to deliver public remarks in Washington following the Supreme Court ruling Thursday.

Romney's promise to repeal the health care law has become a pillar in an agenda that so far offers voters few other specifics. He released a new television ad campaign late last week stressing that the elimination of the health care law will be the top priority in his administration's first 100 days.

Should the court strike down the law, however, attention would turn quickly to what he would do to help 50 million uninsured people get coverage and bring down the nation's spiraling health care costs.

Only about one-third of Americans support the law, according to a recent AP-GfK poll, but 77 percent want the president and Congress to start working on a new health care bill if the Supreme Court rules the 2010 overhaul unconstitutional.

Romney has promised to replace the measure with a handful of "common-sense" reforms, but has spent little time so far crafting a comprehensive plan. He did not address any plans to replace the law Tuesday.

Obama was set to appear Tuesday at two fundraisers in Atlanta, followed by two events in Florida.

Related on HuffPost:

Here are Romney's greatest hits from the campaign:
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  • With A Little Help From My Friends (Joe Cocker)

    <strong><a href="http://www.huffingtonpost.com/2012/05/28/mitt-romney-will-not-repu_n_1551540.html" target="_hplink">(May 28, 2012) --</a></strong> Despite a resurgence of <a href="http://www.thedailybeast.com/articles/2012/05/25/mitt-romney-s-new-bff-donald-trump.html" target="_hplink">Donald Trump's birther claims</a>, Romney refused to repudiate the billionaire, who has been helping with his 2012 campaign efforts. "You know, I don't agree with all the people who support me ... I need to get 50.1 percent or more and I'm appreciative to have the help of a lot of good people," Romney said. (Photo by Ethan Miller/Getty Images)

  • Who Let The Dogs Out (Baha Men)

    <strong><a href="http://www.huffingtonpost.com/2012/04/16/mitt-romney-seamus_n_1429925.html" target="_hplink">(April 16, 2012) -- </a></strong> In an interview with ABC's Diane Sawyer, Romney discussed the political fallout over strapping his dog Seamus to a car roof. He admits that he probably would not do it again. (Handout)

  • It's The End Of The World As We Know It (R.E.M.)

    <strong><a href="http://www.huffingtonpost.com/2012/04/04/mitt-romney-medicare-president-obama_n_1403267.html" target="_hplink">WASHINGTON, D.C. (April 4, 2012) --</a></strong> Speaking before the Newspaper Association of America, Romney attacked Barack Obama on his health record, claiming the president "has taken a series of steps that end Medicare as we know it." (Photo: Jim Watson/AFP/Getty Images)

  • For The Love Of Money (The O'Jays)

    <a href="http://www.huffingtonpost.com/2012/03/14/mitt-romney-i-made-a-lot-of-money_n_1345516.html" target="_hplink"><strong>NEW YORK, N.Y. (March 14, 2012) -- </strong></a> Romney became testy on Fox News while discussing his appeal to lower-income voters. On the same day, Occupy Wall Street protesters staged a demonstration outside Mitt's Waldorf Astoria hotel fundraiser. (Photo: Emmanuel Dunand/AFP/Getty Images)

  • People Are Strange (The Doors)

    <strong><a href="http://www.huffingtonpost.com/2012/03/09/mitt-romney-south_n_1334478.html" target="_hplink">PASCAGOULA, Miss. (March 9, 2012) --</a></strong> While on the trail in Alabama and Mississippi, Romney got in touch with his Southern side, learning how to say "y'all" and liking his grits. With those new experiences in hand, he admitted that "strange things are happening to me." (Photo: AP/Evan Vucci)

  • Pink Cadillac (Bruce Springsteen)

    <a href="http://www.huffingtonpost.com/2012/02/24/mitt-romney-cadillac_n_1299740.html" target="_hplink"><strong>DETROIT, Mich. (Feb. 24, 2012) -- </strong></a> While speaking before the Detroit Economic Club at Ford Field, Romney listed not two, not three, but four American-made cars that he and his wife, Ann, owned. Among the vehicles: "a couple of Cadillacs." (Photo: Scott Olson/Getty Images)

  • It's The Hard-Knock Life (Annie & The Orphans)

    <strong><a href="http://www.huffingtonpost.com/2012/02/01/mitt-romney-very-poor_n_1246557.html" target="_hplink">TAMPA, Fla. (Feb. 1, 2012) --</a></strong> In an interview with CNN, Romney noted that he is "not concerned about the very poor," citing the social safety net for that segment of the populace. (Photo: Ethan Miller/Getty Images)

  • America The Beautiful

    <a href="http://www.huffingtonpost.com/2012/01/31/mitt-romney-america-the-beautiful-_n_1243908.html" target="_hplink"><strong>THE VILLAGES, Fla. (Jan. 31, 2012) --</strong></a> On the eve of Florida's primary, Romney led his supporters in a singing of the patriotic song. (Photo: Emmanuel Dunand/AFP/Getty Images)

  • Successful (Drake, Lil Wayne)

    <a href="http://www.huffingtonpost.com/2012/01/19/mitt-romney-tax-returns_n_1217708.html" target="_hplink"> <strong>CHARLESTON, S.C. (Jan. 19, 2012) -- </strong></a> During CNN's GOP debate, Romney refused to commit to disclosing his tax returns, offering no apologies for his success. (Photo: Emmanuel Dunand/AFP/Getty Images)

  • Bye Bye Bye ('N Sync)

    <a href="http://www.huffingtonpost.com/2012/01/09/mitt-romney-i-like-being-able-to-fire-people_n_1194115.html" target="_hplink"><strong>NASHUA, N.H. (Jan. 9, 2012) -- </strong></a> In a speech about insurance options, Romney tells audience members, "I like being able to fire people who provide services to me." (Photo:AP/Charles Dharapak)

  • Don't Know Why (Norah Jones)

    <strong><a href="http://www.huffingtonpost.com/2011/10/28/mitt-romney-embraces-climate-change-denial_n_1063905.html" target="_hplink">PITTSBURGH, Pa. (Oct. 27, 2011) --</a></strong> Back in June 2011, Romney said humans are somewhat tied to climate change. By October, he had reversed course, saying "We don't know what causes climate change." (Photo: Jim Watson/AFP/Getty Images)