On the campaign trail for president, they can raise their profile from local pol to national voice. They can raise millions, draw crowds, rally the base, needle the front-runners, and maybe, just maybe, start a movement or at least force a dialogue.
It has got to be an exhilarating experience for a fringe presidential candidate who makes a ripple in the crowded field, as Rep. Ron Paul, R-Texas, did this year and Rep. Dennis Kucinich, D-Ohio, did in 2004.
Back at their day jobs in Congress, they are but one of 535. One lone vote, one voice in a fractured chorus. But on the campaign trail they are stars.
But beware members of Congress: Stepping onto the national stage can have serious consequences on the soapbox back home.
Both Paul and Kucinich, rather than being in the hunt for their party's nomination for the presidency, are fighting today for their political lives.
As the eyes of the nation turn to two of the largest states holding presidential primaries this season -- Texas and Ohio -- Arizona Sen. John McCain is expected to officially sew up the Republican nomination and on the Democratic side, it's yet another battle in the long, hard struggle between Sens. Barack Obama of Illinois and Hillary Clinton of New York.
Paul, the Texas congressman who distinguished himself as the only Republican presidential candidate opposing the Iraq War, gained a devoted following, harnessing the power of the Internet to raise more cash than more mainstream rivals, including current front-runner McCain.
But that same anti-war, libertarian bent that gave Paul national recognition could come back to bite him at home.
Paul, who ran for the White House as a libertarian in 1988 but gained more of a following this year as a Republican, has not suspended his presidential campaign, but he has significantly scaled back his national operation to focus on the race at home.
"I do think the presidential race has exposed some of his values and principles that are not in line with his district, and that exposure has done him harm at home," Republican primary challenger Chris Peden said of Paul.
Kucinich, in his sixth term in Congress, suspended his presidential bid -- he also ran in 2004 -- in January to focus on his House race, where he has four challengers in the Democratic primary, though Cleveland City Councilman Joe Cimperman, who calls Kucinich an "absentee congressman," has raised more money than the others.
Back in Texas, Peden, a CPA and city councilman in Friendswood, Texas, said Paul's national campaign has awakened voters in the 14th District to exactly how much of a firebrand Paul is.
"He's a lifelong libertarian," Peden said in a telephone interview recently. "He is only a Republican of convenience, not a Republican of conviction. He's a libertarian who runs as a Republican because a libertarian can't get elected in this district."
Despite calls from his supporters, Paul insists he will not run for president as an independent. But he has pledged to continue his Republican presidential bid, knowing full well that the odds -- and delegate math -- are now firmly against him.