Former President Bill Clinton hits the campaign trail in Florida August 16, stumping for Democratic Congressman Kendrick Meek, in his race to win the party's nod for Senate later this month. Clinton's visit is the latest effort by Democrats to bolster support for veteran candidates in a tough midterm election cycle.

Clinton is expected to join Meek at three rallies in south Florida, two days before President Obama plans to meet with Meek at an as-yet unspecified event. Meek's relationship with Clinton stretches back nearly two decades, when the two met during Clinton's first run for president, and Clinton has already held a handful of fundraisers for Meek's Senate campaign. The congressman in turn campaigned for Hillary Clinton in 2008 in her losing presidential primary run.

The White House has expressed its appreciation for Clinton's efforts on the trail, capitalizing on the president's popularity and influence to back preferred candidates. But Clinton's campaign efforts since leaving office in 2001 have yielded mixed results. In 2002, one of Clinton's most active campaign years, seven of the candidates he supported lost their elections, compared to five who won. The White House enlisted Clinton to persuade Rep. Joe Sestak not to run for the Pennsylvania Senate seat currently held by Arlen Specter; Sestak refused and went on to defeat the incumbent Specter in May's Democratic primary. Clinton is expected to rally for Sestak next week.

Clinton and the Obama White House haven't always seen eye to eye on which candidates to support. The former president endorsed Andrew Romanoff in Colorado for the U.S. Senate over incumbent Sen. Michael Bennett, whom Obama supports.

Still, Clinton may be a better big-name option for many incumbent Democrats than the sitting president.

The mood of the country's voters has swayed since Democrats gained control of Congress and the presidency, and many are rejecting what they see as failed efforts on job creation and other policies in a still-weak economy. Many Democratic candidates have distanced themselves from the party's leaders in effort to separate their platforms from the negative image voters may have of the Democrats in charge.

Meek currently trails his opponent, billionaire Jeff Greene, a Washington outsider, by 10 points in the latest Quinnipiac University poll.