All 65 state House seats and 20 of the 35 Senate seats are up for election this year, but in the end it's all about a handful of races, the majority of which are in Arapahoe and Jefferson counties.
Those contests will determine which party controls the House and the Senate for the next two years.
Democrats currently hold a 20-15 majority in the Senate, while Republicans have a 33-32 edge in the House.
Gov. John Hickenlooper, a Democrat, said he didn't want to venture a guess as to how the partisan makeup of the legislature might change after this election.
"There are an awful lot of close races," Hickenlooper said, "so I would invoke that great Denver journalist, Damon Runyon, when he said, 'The race goes not always to the swift nor the battle to the strong, but that's the way to bet.' "
Jefferson County, a swing county in a swing state, is host to several of the most critical legislative races for both parties.
"You feel like you're in the epicenter of all the activity," said Rep. Ken Summers, R-Lakewood, who is challenging Rep. Andy Kerr, D-Lakewood, for a new Senate seat. "As a candidate, you're almost bowled over."
Republicans have to win all four of their most competitive races in the Senate in order to take the majority, something that seemed impossible until the first presidential debate Oct. 3 in Denver. Pundits declared Republican Mitt Romney the winner over President Barack Obama, and volunteers the next day flooded Romney's headquarters in Jefferson County and elsewhere in the state.
Republicans are counting on that surge of excitement to help them win their legislative races.
"Having a strong top of the ticket helps us," said House Speaker Frank McNulty, R-Highlands Ranch.
But pundits say it will be hard for House Republicans to defend their majority, not only because of having just a one-seat advantage but also due to fallout from a failed civil-unions bill and how district boundaries were redrawn during reapportionment last year.
For example, state Rep. Cindy Acree of Aurora went from one of the safest Republican seats in the metro area to one that now favors her Democratic challenger, former school principal John Buckner.
Mario Nicolais, a Lakewood attorney and a Republican who served on the commission that redrew legislative boundaries, believes Democrats packed Republicans into districts.
"That's the main reason we opposed the House maps so vigorously," he said.
Nicolais pointed out that Democrats have the edge in both House seats in Lakewood. Republicans were willing to make one seat a safe Democratic seat as long as the other was 50-50 but lost the argument, he said.
Those two Lakewood seats are among the contests crucial to determining whether McNulty remains speaker or whether that post goes to the current House minority leader, Democrat Mark Ferrandino of Denver.
Ferrandino said the final legislative boundaries were more favorable to Democrats than the maps Republicans appealed to the Colorado Supreme Court.
"If they're upset about the maps, they should look in the mirror," he said.
"I don't think anybody on our side thinks the first maps were more favorable," McNulty countered.
Ferrandino co-sponsored the bill that would have allowed gay couples to form civil unions. Backers were outraged that the speaker refused to call it up for debate, ensuring its death on the second-to-last night of the legislative session.
Nicolais, spokesman for Coloradans for Freedom, a GOP group supporting civil unions, said at the time he was worried about the impact on the November election. He feared Democrats would marshal extra resources to take back the majority, a worry he said has borne out.
The group Fight Back Colorado was formed in response to what happened with civil unions. It has spent $215,000 attacking three Republicans: Reps. Acree, Robert Ramirez of Westminster and J. Paul Brown of Ignacio.
As for the Senate, Nicolais agreed with those who said the Senate map was drawn in such a way that Republicans could pick up seats this year and will be in good shape in 2014.
"One of the reasons that you see so much money and emphasis being placed for Democrats this year is they realize they have only a two-year window and the Senate will be difficult for them to control going forward," Nicolais said. "If Republicans don't control the Senate after 2014, there's really no one to blame but themselves because the districts really do favor them."
A handful of races will determine which party controls the state House and Senate after Tuesday. Here are some of them:
Sen. Evie Hudak, D-Westminster, vs. Lang Sias of Arvada
Dem Rep. Andy Kerr vs. GOP Rep. Ken Summers, both of Lakewood
Sen. Linda Newell, D-Littleton, vs. GOP Dave Kerber of Greenwood Village
GOP Larry Crowder of Alamosa vs. Dem Crestina Martinez of San Acacio
Rep. Daniel Kagan, D-Cherry Hills Village, vs. GOP Brian Watson of Greenwood Village
Dem Rep. Pete Lee vs. Jennifer George, both of Colorado Springs
GOP Rep. Mark Barker vs. Dem Tony Exum, both of Colorado Springs
Dem Rep. Max Tyler vs. GOP Rick Enstrom, both of Lakewood
GOP Amy Attwood vs. Dem Brittany Pettersen, both of Lakewood
Rep. Robert Ramirez, R-Westminster, vs. Dem Tracy Kraft-Tharp of Arvada
GOP Rep. Cindy Acree vs. Dem. John Buckner, both of Aurora
Dem Chuck Rodosevich vs. GOP Clarice Navarro-Ratzlaff, both of Pueblo
Rep. J. Paul Brown of Ignacio vs. Dem Mike McLachlan of Durango