PIERRE, S.D. — U.S. Sen. Tim Johnson of South Dakota on Wednesday left open the possibility he will not seek re-election in 2014.

After former Republican Gov. Mike Rounds said last week he would run for the seat now held by Johnson, the Democrat responded with a statement saying "I fully intend to put together a winning campaign in the weeks and months ahead."

But in a telephone press conference with South Dakota reporters on Wednesday, Johnson said his earlier statement should have been more clear about the prospects he will seek a fourth term.

"If I run again, I will run a strong campaign is what I meant. But only if I run again, and it's far too soon to make that statement," Johnson said.

The 65-year-old senator said he will announce sometime next year whether he will run.

Johnson's health problems have led to speculation he might not seek re-election. He had surgery in 2006 for bleeding in his brain, which has slowed his speech and required him to sometimes use a motorized scooter when he needs to get around quickly.

The senator said he is capable of enduring the rigors of a campaign and his health will not play a role in whether he seeks re-election.

"I'm good to go. I feel great," Johnson said.

Johnson said he proved he is healthy enough to campaign when he won re-election in 2008, two years after the surgery to stop bleeding caused by arteriovenous malformation, a condition that causes arteries and veins in the brain to grow abnormally large, become tangled and sometimes burst.

South Dakota Democratic Party Chairman Ben Nesselhuf said he never thought Johnson's remarks last week meant he was certain to seek re-election, but Democrats for now are looking at Johnson as their 2014 Senate candidate.

"Until he tells me otherwise, he's my guy. I have every reason to believe he would run just one heck of a campaign," Nesselhuf said.

But if Johnson decides to retire, Democrats will find other strong candidates for the Senate seat, Nesselhuf said. Former Democratic Rep. Stephanie Herseth Sandlin and the senator's own son, U.S. Attorney Brendan Johnson, have been mentioned as possible candidates.

Also on HuffPost:

Loading Slideshow...
  • Harry Reid (D-Nev.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 110th-112th Congress (2007-present)

  • Bill Frist (R-Tenn.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 108th & 109th Congress (2003-07)

  • Tom Daschle (D-S.D.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 107th Congress (2001-03)

  • Trent Lott (R-Miss.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 105th & 106th Congress (1997-2001)

  • Bob Dole (R-Kan.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 99th & 104th Congress (1985-87, 1995-96). Dole resigned from the Senate in June 1996 to focus on his presidential campaign.

  • George Mitchell (D-Maine)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 101st-103rd Congress (1989-95)

  • Robert Byrd (D-W.V.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 95th, 96th & 99th Congress (1977-81, 1985-87)

  • Howard Baker (R-Tenn.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 97th & 98th Congress (1981-85)

  • Mike Mansfield (D-Mont.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 87th-94th Congress (1961-77)

  • Lyndon Johnson (D-Texas)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 84th-86th Congress (1955-61). Johnson resigned from the Senate in Jan. 1961 to take on his new role as vice president.

  • William Knowland (R-Calif.)

    (Pictured right) <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 83rd Congress (1953-55)

  • Robert Taft (R-Ohio)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 83rd Congress (1953). Taft died on July 31, 1953 and William Knowland was elected to take over on August 4.

  • Ernest McFarland (D-Ariz.)

    (Pictured standing, far right) <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 82nd Congress (1951-53)

  • Scott Lucas (D-Ill.)

    (Pictured front row, left) <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 81st Congress (1949-51)

  • Wallace White Jr. (R-Maine)

    (Pictured far left) <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 80th Congress (1947-49)

  • Alben Barkley (D-Ky.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 75th-79th Congress (1937-47).

  • Joseph Robinson (D-Ark.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 73rd-75th Congress (1933-37). Robinson died on July 14, 1937, and Alben Barkley was elected a week later to take over.

  • James Watson (R-Ind.)

    (Pictured second from right) <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 71st & 72nd Congress (1929-33)

  • Charles Curtis (R-Kan.)

    <a href="http://www.senate.gov/artandhistory/history/common/briefing/Majority_Minority_Leaders.htm#2">Senate Majority Leader</a>, 68th-70th Congress (1923-29). Curtis resigned from the Senate in March 1929 after being elected vice president.