(Updated 11:30 a.m., Mon., July 28)

U.S. Sen. Claire McCaskill, D-Mo., has underscored her influence within the Missouri Democratic Party by writing a check for $240,000 – making her the new top donor for the party.

And wealthy financier Rex Sinquefield has donated another hefty sum to one of his favorite officeholders, St. Louis County Executive Charlie Dooley.

But Sinquefield gave even more Monday to a Republican rival for Dooley's job, state Rep. Rick Stream.

McCaskill’s check, posted on the Missouri Ethics Commission’s website Sunday, surpasses the $200,000 that the state Democratic Party previously received from Missouri Attorney General Chris Koster, the Republican-turned-Democrat who’s now running for governor in 2016.

State Democratic Party chairman Roy Temple said in a statement Monday that the money was raised Friday night. "We had a phenomenal event at the senator's home to raise money for our legislative efforts and are thrilled with both the success of the event and her personal commitment to the effort."

McCaskill and Koster, political allies, have been wielding more influence over the state party's operations since last year. Both have said they're committed to helping Temple in his efforts to pour more money into state legislative races this fall. Democrats are heavily outnumbered in the state House and Senate.

McCaskill has been publicly critical of Republicans controlling the Missouri General Assembly, saying many of their views of out of step with average Missourians -- a jab that the GOP often makes about her.

Bill Greenblatt | UPI | File photo Sen. Claire McCaskill.

McCaskill’s money made up most of the $335,000 that the state party collected from checks that came in Friday, according to the commission’s website.

The second-largest donation came from the campaign account of House Minority Leader Jake Hummel, D-St. Louis, who recently took the No. 2 position within the Missouri AFL-CIO. Hummel plans to keep his legislative seat and is running for re-election this fall.

Sinquefield makes last-minute entry in county executive contest

Meanwhile, Sinquefield appears to be playing both sides in the region's hottest political contest this year.

On Monday, the Missouri Ethics Commission reported that Sinquefield donated $100,000 to Stream, who is competing against Tony Pousosa, a Green Park alderman, in the Republican primary for county executive.

Dooley collected $50,000 late Friday from Sinquefield, who long has been among Dooley’s top donors. The latest donation is in addition to $346,000 donated since 2009 by Sinquefield or his wife, Jeanne Sinquefield. She donated $100,000 to Dooley earlier this year.

Sinquefield’s latest check could help pay for more ads or field operations for Dooley, who is in a tight battle with Councilman Steve Stenger in the Aug. 5 Democratic primary. Stenger has been receiving most of the region’s labor donations, a top money source for many Democrats.

Sinquefield wants to eliminate Missouri’s income tax and also advocates private-school vouchers – two stances apparently not shared by Dooley.

Sinquefield’s support for Dooley apparently stems, in part, from their like-minded views in favor of a closer relationship between St. Louis and St. Louis County.

Dooley has said that it’s up to the voters to decide whether the city should be allowed to re-enter the county – ending a split that began in 1876. But he has approved a merger of the two bodies’ economic-development agencies and has backed other cooperative efforts.

Stream, by the way, has not been enthusiastic about any merger talk.