IOWA CITY, Iowa — Republican Gov. Terry Branstad's re-election campaign is starting 2014 with more than 17 times as much money in the bank as his likely Democratic opponent, state Sen. Jack Hatch.

The money disparity marks another challenge in Hatch's uphill bid to unseat Branstad, who has never lost an election and is seeking an unprecedented sixth term as governor.

Hatch's campaign reported Sunday that it had nearly $237,000 in the bank after expenses as of Dec. 31. Hatch, a Des Moines Democrat and owner of the Hatch Development Group, raised about $300,000 from donors in 2013. Hatch and his wife, Sonja Roberts, loaned the campaign a total of $140,000.

Branstad campaign spokesman Tommy Schultz said the campaign will report Tuesday — the filing deadline — that it had $4.1 million in the bank as of Dec. 31, which would be the most ever at the end of a reporting period by an Iowa gubernatorial candidate. The governor officially declared last week that he would seek re-election in November and embarked on a series of campaign events.

"We've seen a diverse array of folks from all across Iowa donating to Gov. Branstad and Lt. Gov. Reynolds. We're excited about that show of support," he said.

Hatch became the Democratic Party's likely nominee to face Branstad last month, when his primary challenger, state Rep. Tyler Olson of Cedar Rapids, dropped out of the race amid marital problems. Another candidate, Bob Krause, has dropped out and endorsed Hatch.

Branstad is a heavy favorite to win re-election.

Democratic strategist Jeff Link, who is not working for the Hatch campaign, said the key for Hatch is not to outspend Branstad but to raise enough money to introduce himself to voters and contrast himself with the governor. He said Hatch will need to have $3 million to $4 million to spend from the summer through the November election to meet that threshold.

"His new status as presumptive nominee will help his fundraising significantly," Link said.

Hatch campaign spokesman Grant Woodard agreed. He said that with Olson's decision to drop out, the campaign has an opening to raise larger sums from labor unions and other traditional Democratic Party supporters who were reluctant to get involved in a competitive primary.

Woodard said the campaign will seek to capitalize on polls showing Iowans may like Branstad but believe he has been in office too long.

"We'll be traveling and making our case to Democratic Party allies on why they should invest in this race," he said. "I think we have the opportunity to raise a lot more money."

Hatch's campaign filing shows that Des Moines-area business leaders who have donated heavily to Democrats in the past, such as Fred Hubbell and Bill Knapp, made contributions. The largest single donors were Cedar Rapids businessman Roy Karon and Omaha philanthropist Richard Holland, who gave $25,000 and $20,000, respectively. Hatch relatives, including a brother, a sister, a cousin and an aunt, gave a combined $20,500.

Details on Branstad's individual donors are expected to be made public Tuesday.