AURORA, COLO. ? Colorado Republicans are hosting a campaign tea party this fall, for better or worse.

Or maybe for better and worse, in a jarring demonstration of the potential and peril generated by a political movement responsible for reshaping the 2010 election season.

One statewide nominee, Ken Buck, won the primary with the support of tea party activists and is a modest favorite to defeat appointed Democratic Sen. Michael Bennet. He enjoys the full backing of the Republican Party, and the groups aligned with it are pouring millions into television ads to help him.

The other, Dan Maes, went into a political nosedive soon after his surprise victory in the gubernatorial primary and has yet to recover. His personal credibility challenged, he’s been labeled an embarrassment by the state party chairman and overshadowed by a third-party contender.

Tea party activists in Colorado “provided much of the passion for the primaries on Aug. 10,” said Floyd Ciruli, a Denver pollster. At the same time, “they have changed what it means to be conservative” with their eagerness to recommend changes to Social Security and calls for shuttering federal departments.

That willingness, in turn, nourishes a Democratic strategy of labeling Buck and others as extremists, part of a nationwide strategy aimed at persuading voters to look past economic woes when voting this fall.

The same grass-roots passion that propelled two tea party contenders in Colorado has left a mark elsewhere, with similarly uncertain results for Nov. 2.

In Kentucky, Republicans quickly made peace with Rand Paul after he defeated an establishment-backed nominee in the Senate primary. But the race is tight in the public polls, and party officials have worried for months that the first-time candidate may prove too controversial or undisciplined to prevail.

In Arizona, Jesse Kelly surprised the GOP leadership by winning the nomination to challenge Democratic Rep. Gabrielle Giffords. Despite the potentially competitive nature of the seat, Republicans have yet to launch the type of costly ad campaign they are running in dozens of other districts.

In Maine, a state represented by two of the Senate’s most moderate Republicans, gubernatorial candidate Paul LePage steers a more conservative fiscal course and occasionally stirs the kind of controversy they avoid. Polls depict an unpredictable multicandidate race a little more than two weeks before Election Day.

In Colorado, Maes put his conservatism on display over the summer when he said a Denver bike-sharing program was part of a “greater strategy to rein in American cities under a United Nations treaty.”

A political novice, he won the gubernatorial nomination when the campaign of a better-known rival, former Rep. Scott McInnis, collapsed in a plagiarism controversy.

Before he could pivot to the fall campaign against Denver’s Democratic Mayor John Hickenlooper, Maes struggled to answer questions about his resume. He claims that he was fired by the police department in Liberal, Kan., in the 1980s because police and politicians were corrupt and that he worked undercover for state investigators. The Kansas Bureau of Investigation denies he worked for them.

Maes must contend with a late entry into the race, former Republican Rep. Tom Tancredo, a staunch opponent of illegal immigration running as a candidate of the American Constitution Party.

Dick Wadhams, the GOP state party chairman, described Maes in an interview as “the worst candidate in Colorado history we’ve ever had for governor and one of the most polarizing.”