Democratic candidates outraised Republicans incumbents in more than two dozen competitive House races in the first quarter of 2018, a continuation of their strong fundraising last year and a signal of a potentially large field of seats in play this fall.

In more than half a dozen of those races, a Democratic challenger ended the first quarter with more cash in the bank than the incumbent, a major source of concern for Republicans at this point in the cycle.

The races vary in degrees of competitiveness, according to ratings from the nonpartisan Cook Political Report. Democratic challengers outraised GOP incumbents in eight races considered tossups, seven races considered to lean Republican, and 13 races that are likely Republican but still competitive, according to a RealClearPolitics review of campaign finance filings.

But there were strong signs for Republicans in the first quarter fundraising numbers as well. Several candidates whom party operatives were concerned about last year improved their fundraising totals this quarter, and GOP lawmakers in some of the most competitive districts in the country raised hefty sums, giving them significantly larger war chests than their opponents.

Still, Democrats in several highly competitive races outpaced their Republican opponents. In Minnesota, Democrat Angie Craig (pictured) nearly doubled Rep. Jason Lewis’ total for the quarter in a rematch of a competitive race last cycle, and she significantly narrowed his total cash advantage. In New York, state Assemblyman Anthony Brindisi significantly outraised GOP Rep. Claudia Tenney and had a cash advantage of more than $200,000. In southern Illinois, Democrat Brendan Kelly emerged from his primary last month with most of his fundraising total intact, and only narrowly trailed GOP Rep. Mike Bost.

In North Carolina, Democrat Dan McCready nearly doubled the fundraising total of Rep. Robert Pittenger, and has more than four times as much cash in the bank as the Republican incumbent, who faces a primary challenge. Similarly, Democrat Kathy Manning more than doubled Rep. Ted Budd’s fundraising haul so far this year, and has nearly double his cash on hand.

In Pennsylvania, Conor Lamb – the Democrat who won a special election last month in a heavily pro-Trump district – ended the quarter with more cash than GOP Rep. Keith Rothfus, whom Lamb is challenging this fall after district lines were redrawn.

Tyler Law, a spokesman for Democrats’ House campaign committee, said challengers were “outworking and out-organizing” Republicans.

“The reality is that a significant number of Republican incumbents have proven complacent and unable to locate those old campaign muscles,” Law said. “In contrast, Democratic campaigns are fueled by a surge of energy and grassroots donations, ensuring that they will have the resources needed to tell their stories and outline their records of service to voters.”

But there were encouraging signs for Republicans. Florida Rep. Carlos Curbelo, one of the party’s most vulnerable members, outraised his challenger and has more than $2 million in the bank, a significant advantage. Rep. Barbara Comstock of Virginia, who is also considered a top target, raised more than double every Democrat in the crowded primary to challenge her, and had nearly $2 million in the bank.

Republicans hope that in districts such as Comstock’s, Democrats will emerge from competitive primaries having spent most of their cash, giving the incumbents a major head start in fundraising for November.

In two competitive Texas districts, GOP incumbents amassed more than $1.5 million in the bank while all four Democrats in the May primary runoff had less than half a million dollars. Rep. John Culberson, who represents a Houston district and had frustrated party strategists last year with his sluggish campaign, posted his best fundraising quarter and ended with nearly $1 million, a significant advantage over whichever Democrat faces him after the May runoff.

In Illinois, Sean Casten emerged from a crowded primary to challenge GOP Rep. Peter Roskam, who represents a suburban district that Hillary Clinton won by seven percentage points in 2016. But Roskam has more than $2 million in his war chest, while Casten emerged with just under $200,000 after the primary.

“House Democratic candidates in competitive districts all throughout the country are going to be forced to spend an enormous amount of money informing voters of how progressive they are just to be able to capture the Democratic nomination,” said Jesse Hunt, spokesman for House Republicans campaign committee. “The positions they’ll take and resources they’ll expend will render them unelectable when it comes time for the general election.”

Candidate fundraising is an important indicator of enthusiasm and grassroots support for candidates, as well as the strength of each candidate’s organization, though it is just one of many measures to gauge the competitiveness of a race. Candidate fundraising is also critical because campaigns are able to purchase TV advertising at a lower rate than outside groups, though both parties are likely to invest significant outside resources in these races.

Congressional Leadership Fund, a super PAC allied with Speaker Paul Ryan, announced Tuesday it would spend $48 million in advertising in key House districts for the fall, including several where Republican candidates were outraised, though that likely represents just the initial amount the group will spend. House Majority PAC, the top Democratic outside group focused on the lower chamber, announced its initial booking of $40 million in fall ads last month.