Republican Donald Trump and Democrat Hillary Clinton look to build on their leads in the presidential nominating races when four states vote on Tuesday, and polls show both front-runners comfortably ahead in the biggest prize of Michigan.
Trump hopes to regain his momentum after suffering a week of blistering attacks from the party's establishment and splitting four contests on Saturday with rival Ted Cruz, who positioned himself as the prime alternative to the brash billionaire in the race for the party's nomination for the Nov. 8 election.
Most opinion polls show Trump hanging on to a solid double-digit lead in Michigan over Cruz, a U.S. senator from Texas, and Ohio Governor John Kasich.
The establishment favorite, U.S. Senator Marco Rubio of Florida, lags behind and is seen needing a breakthrough win in his home state next week to keep his campaign alive.
Republicans and Democrats will also vote in Mississippi, and Republicans in Idaho and Hawaii will make their choices on a day when 150 Republican delegates and 166 Democratic delegates will be up for grabs.
But the focus on Tuesday is the industrial battleground of Michigan, where Trump's relentless anti-free trade rhetoric and promise to slap taxes on cars and parts shipped in from Mexico has resonated in a state that has lost tens of thousands of manufacturing and auto industry jobs.
"Trump has been holding strong and no one seems to be catching up," said Republican pollster Steve Mitchell, whose latest Fox 2/Detroit poll on Sunday showed Trump with a 22-point lead on Cruz and Kasich.
"The anti-Trump vote is being divided almost evenly, and neither of them can get an edge," he said.
Among Democrats, Clinton, 68, also has a solid double-digit lead in Michigan opinion polls over rival Bernie Sanders, 74, a U.S. senator from Vermont. The former secretary of state is also expected to do well in Mississippi, where the Democratic electorate will be dominated by black voters who have overwhelmingly favored her over Sanders.
Big Michigan wins for Trump and Clinton would set them up for a potentially decisive day of voting on March 15, when the delegate-rich states of Ohio, Florida, Illinois, Missouri and North Carolina cast ballots.
The Republican contests in Florida and Ohio award all the state's delegates to the winner. If Trump, 69, could sweep those two states and pile up delegates elsewhere, it would probably knock home-state favorites Rubio and Kasich out of the race and make it tough for Cruz to catch him.
'ALL TALK, NO ACTION'
Trump, a blunt-spoken political outsider who has been under relentless attack from establishment figures and Super PACs since winning seven of 11 races on Super Tuesday last week, launched his own attack ad against Rubio, calling him a "corrupt, all-talk, no-action politician."
"That guy, he couldn't be elected dogcatcher in Florida," Trump told supporters in North Carolina.
Trump has so far won 384 delegates to 300 for Cruz, but the contests over the next week will play a big role in determining whether any candidate gathers the 1,237 needed to win the nomination or if the decision will have to be made at the convention in July.
In the Democratic race, Clinton has built a lead of nearly 200 pledged delegates over Sanders, and the party's rules awarding delegates proportionally in all states will make it hard for him to catch up because she can keep piling up delegates even in states she loses.
The two candidates spent Monday campaigning in Michigan, one day after their debate in Flint that featured sharp clashes on free trade agreements and the auto bailout.
They resumed their battle on Monday, with Sanders accusing Clinton of distorting his record when she said he opposed the auto bailout credited with rescuing General Motors and Chrysler during the economic crisis.
Sanders, a democratic socialist, said he supported the bailout and voted for it in the Senate, but that bill failed to win approval. He later voted to block auto bailout funds because they were combined with funds to bail out Wall Street.
Sanders released a radio ad on Monday saying Clinton was trying to distort his record. Sanders, the ad said, "has always been on the side of Michigan workers and working families."