DENVER (AP) — As Colorado House lawmakers churned through final votes during the last night of this year's session, Republicans stood up and marched out of the chamber before the Democratic speaker could gavel it to a close — a defiant act meant to show how sidelined and silenced they felt.

The political theater this week was the culmination of a 120-day session that proved to be the latest illustration of the leftward shift in what was long a battleground state, leaving Republicans scrambling to adjust to their unfamiliarly weak position and surfacing internal rifts among Democrats over just how progressive Colorado should be.

The shift has been partly driven by migration to Colorado and the transformation of white, college-educated voters — a disproportionate share of the state's electorate — into Democratic supporters during the Trump era. The last Republican presidential candidate that Colorado voters backed was George W. Bush in 2004. The current governor, both U.S. Senators and five of the eight members of the U.S. House are Democratic.

With Democrats also in control of two-thirds of seats in the state House and Senate, the largest majority for the party in decades, Republicans have often resorted to delay tactics this session. One filibuster ran for 18 hours and spilled into the next morning. Sometimes Republicans asked that bills be read at length, and an electronic voice would drone through byzantine language for hours.

Yet they were unable to stop Democrats from passing the state’s largest gun control package and codifying protections for abortion and transgender rights.

To help pass those bills, House Speaker Julie McCluskie invoked a rarely used rule curtailing filibusters, arguing that the debates had become unproductive and merely stall tactics. Republicans decried it as a gag measure.

“What we saw through this session is ... an overwhelming amount of power,” Minority Leader Rep. Mike Lynch said, calling Republicans' position a “superminority.”

“It makes it really hard to find out how we can still contribute to our districts,” he added, and said Monday's walkout was necessary to send a statement because “We were out of tools."

But even while Democrats swung their weight around — passing four gun control bills including one that raised the minimum purchasing age for all firearms from 18 to 21 — they drew the line on a number of progressive policies.

A sweeping ban on semi-automatic firearms was killed in committee by Democrats. Another that would have allowed “ safe injection sites,” where people can use illicit drugs under the supervision of trained staff who could reverse an overdose, also went nowhere.

Democratic Senate Majority Leader Dominick Moreno, who has been in the Legislature since 2013, said Colorado is on a blue trajectory but he still considers its political tint to be “a shade of purple, indigo maybe.”

While registered Democrats outnumber Republicans by over 120,000, unaffiliated voters exceed both, signaling the state’s independent streak.

Colorado is the only state in the union to cap government spending, a relic of its conservative past that maintains broad support among voters. It was also the first state to legalize marijuana, a measure supported by many of the state’s live-and-let-live Republicans. Many of those have since switched parties, and Gov. Jared Polis, who won with nearly 60% of the vote, is a libertarian-leaning Democrat.

Republican leadership hopes the party could get a boost in turnout next election if constituents believe Democrats went too far while in the majority: “The overreach is palpable,” said Sen. Paul Lundeen, the Senate minority leader, “the people will respond in a meaningful way.”

But Colorado doesn't figure to flip back to red anytime soon, said Seth Masket, director of the Center on American Politics at the University of Denver, especially with the biggest population growth coming in the blue-leaning urban corridor along the east side of the Rocky Mountains including Denver and its sprawling suburbs.

Amid a national political environment tilting toward partisan extremes, Masket said, the leftward shift tends to snowball as many people choose when possible to live in places that reflect their values and beliefs.

“Is it easier or harder to get an abortion? Is it easier or harder to get a gun? All these things really affect people’s lives, and once a state has a reputation for being relatively blue, it will attract more people like that,” Masket said.

A signal of Democrats' growing power is that the state's defining political battles are bubbling up internally among the party rather than with the GOP, he said: “That’s where the locus of power is.”

That dynamic has been around longer in deep blue states such as California and New York but is relatively new to Colorado, which has less of a history of sharp partisan clashes, and more cross-aisle amity.

Assistant Minority Leader Sen. Bob Gardner, a Republican, reflected in a press conference Tuesday on his past sessions as a representative, saying "we were in a fairly deep minority but frankly our friends across the aisle and ourselves were a good deal closer politically than we are today.”

While remnants of that amiability remain, they can occasion frustration among progressive Democrats who see little need to compromise anymore.

That was on display in an exchange at the Democrats' last caucus meeting Monday, after progressive Rep. Elisabeth Epps admonished Speaker Julie McCluskie for giving GOP lawmakers too much leeway in both their rhetoric and delay tactics.

“I am committed to your success, and the success of every individual in this room, and truthfully the success of our Republican colleagues, that is what this job is,” McCluskie replied. “I truly believe in this institution and what it means to work through a Democratic process that is messy.”

Her comments drew applause from roughly two-thirds of the caucus, but there was also disagreement.

“There is a point at which we need to stop acting like trying to get along with our enemies is going to preserve our institution,” said Rep. Stephanie Vigil, another progressive.

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Jesse Bedayn is a corps member for the Associated Press/Report for America Statehouse News Initiative. Report for America is a nonprofit national service program that places journalists in local newsrooms to report on undercovered issues.