Iowa Gov. Terry Branstad (R). (Charlie Neibergall/AP)

DES MOINES — Iowa politics is best known for its influence on the presidential nominating process. But two years before the next set of caucuses, the state’s political establishment is gearing up for big battles over a rare open Senate seat, two competitive open seats in the U.S. House and control of the state legislature. Even though Gov. Terry Branstad (R) appears set on a glide path to a record sixth term, the busy political season has put a curb on most legislative business.

Debates over taxes, both corporate and personal, are likely to take center stage.

The Republican-controlled state House will push to cut income taxes at a time when the economic recovery is spurring growing revenue. Branstad said last month he is considering pushing an optional flat tax. But both proposals are likely to stall in the Democratic-controlled Senate.

“I don’t know that the Senate, particularly the Senate leadership, is quite ready to [cut income taxes], but we’re going to talk about it,” Kraig Paulsen, the Republican Speaker of the House, said at a fundraising breakfast previewing his session agenda on Monday. Senate Republican leader Linda Upmeyer downplayed the chances of passing an income tax cut, saying in an interview that “it always takes a few years on a big lift like that.”

But action is likely on a handful of tax credits, after the state’s Economic Development Authority proposed ending an Enterprise Zone program and boosting funding for a program aimed at creating new jobs. Smaller rural areas are worried that the end of the Enterprise Zone program would hurt their prospects for new development money.

Neither Democrats nor Republicans will propose major increases to the state budget. Iowa maintains about $1 billion in its rainy day fund and expects to have a surplus of $600 million to $700 million. Branstad will tout that surplus as he campaigns for reelection this year, while Republicans said they will focus on holding the line on spending.

“It only takes one bad budget to undo all the good we’ve done,” Upmeyer said.

The races for federal offices will dominate the political landscape in Iowa this year, especially given the rarity of an open seat. Tom Harkin’s (D) Senate seat hasn’t been vacant since Sen. Thomas Martin (R) retired in 1960; the state’s other seat, held by Sen. Chuck Grassley (R), hasn’t been open since Sen. Harold Hughes (D) retired in 1974.

Republicans face a crowded primary. State Sen. Joni Ernst (R), former energy executive Mark Jacobs (R), former U.S. Attorney Matt Whitaker (R), and conservative radio talk show host Sam Clovis (R) mingled with Republican lawmakers and lobbyists at Monday’s session preview at a Des Moines hotel. The winner of the June 3 primary will face Rep. Bruce Braley, the almost-certain Democratic nominee, in November.

Braley’s First District, in the northeast corner of the state, has attracted five prominent Democratic candidates and at least two Republicans; the district gave President Obama 56 percent of the vote in 2012.

Rep. Tom Latham’s (R) retirement has attracted a crowded Republican field in the Third District, which includes Des Moines; last week, Secretary of State Matt Schultz (R) became the latest candidate to jump into the race. Democrats are coalescing behind former state Sen. Staci Appel (D) in a district that gave Obama 51 percent of the vote.