U.S. Sen. Cory Gardner raised $2 million for the three-month period ending June 30, his campaign said Thursday, bringing the Colorado Republican’s total fundraising for his 2020 re-election campaign to $6.6 million. He had $4.9 million in the bank at the end of the quarter.

Considered one of the most vulnerable GOP senators up for election in 2020, Gardner hauled in more than the individual fundraising totals released by any of the Democrats seeking to unseat him – though the two leading challengers together appear to have outraised the incumbent with a reported $2.7 million in contributions for the quarter.

“Senator Gardner’s strong fundraising quarter allows him to continue to build the necessary resources to defeat whichever far-left candidate the Democrats nominate next June,” said Gardner campaign manager Casey Contres in a statement.

Added Contres: “His bipartisan record of results for the state resonates with Coloradans. Our campaign will make sure every Coloradan knows how Sen. Gardner’s commonsense conservative solutions have benefited our state.”

Of the 11 Democrats running for Gardner’s seat, only three have released their fundraising totals or filed campaign finance reports for the most recent quarter. Reports are due to the FEC by midnight July 15.

Former state Sen. Mike Johnston’s campaign said last week that the Denver Democrat took in $1.6 million for the second quarter, making for a $3.4 million total since launching his campaign in January. Johnston didn’t say how much cash he had left over at the end of the fundraising period.

Dan Baer, a former diplomat, said his campaign raised $1.1 million for the quarter, his first in the race, bringing Baer’s total contributions to $1.35 million, including about $250,000 left over from a 2016 congressional run.

According to her FEC report filed on Wednesday, climate activist Diana Bray raised $72,514 for the quarter and had $26,008 in the bank.

Yet to report their fundraising totals are former Colorado House Speaker Andrew Romanoff, who raised just over $500,000 for the first quarter, along with several candidate who got in the race after the start of the most recent fundraising period – former U.S. Attorney for Colorado John Walsh, former Colorado House Democratic Leader Alice Madden and former congressional candidate Stephany Rose Spaulding.

Others running include first-time candidates scientist Trish Zornio, community organizer Lorena Garcia and economist Ellen Burnes.

State Sen. Angela Williams, D-Denver, jumped in the crowded primary this week. Her fundraising strength won’t be evident until after the third quarter, which ends Sept. 30.

Gardner is one of only two Republican senators seeking re-election in states won by Democrat Hillary Clinton, who took Colorado’s electoral votes by about a 5% margin.