[5] After six years out of politics, Walberg ran in a field of six candidates in the 2004 Republican primary for the 7th District after six-term incumbent Nick Smith retired.

[9][10][11] Entering the 2008 race, Democratic Congressional Campaign Committee chairman Chris Van Hollen identified Walberg as one of the most vulnerable Republican incumbents in Congress.

[13] The previous occupant of the seat, Joe Schwarz, who lost to Walberg in the 2006 Republican primary, declined to run but on September 30 endorsed Schauer.

[21] Walberg defeated Doug North in the August 2 Republican primary and Democratic nominee State Representative Gretchen Driskell[22] in the general election, with 55% of the vote.

[36] Walberg also cosponsored a resolution disagreeing with the Supreme Court decision in Obergefell v. Hodges, which held that same-sex marriage bans violated the constitution.

"[38] On October 8, 2023, Walberg gave a keynote speech at the National Prayer Breakfast in Uganda, at the invitation of Ugandan legislator David Bahati.

Walberg additionally praised Uganda's President Yoweri Museveni, who also spoke at the breakfast, and who signed the Anti-Homosexuality Act into law.

[43] In December 2020, Walberg was one of 126 Republican members of the House of Representatives to sign an amicus brief in support of Texas v. Pennsylvania, a lawsuit filed at the United States Supreme Court contesting the results of the 2020 presidential election, in which Joe Biden defeated[44] incumbent Donald Trump.

The Supreme Court declined to hear the case on the basis that Texas lacked standing under Article III of the Constitution to challenge the results of an election held by another state.

[45][46][47] In March 2024, responding to a question about "why are we spending our money to build a port for them,"[48][49] referring to the Biden Administration's plan to build a temporary port off the coast of Gaza to facilitate delivery of humanitarian aid in the Israel-Hamas War,[49][50] Walberg told the crowd the U.S. "shouldn’t be spending a dime on humanitarian aid" and instead “should be like Nagasaki and Hiroshima.

"[48][49][50] The Council on American-Islamic Relations, a U.S.-based Muslim civil rights group, condemned Walberg's comments as a "clear call to genocide.

"[51] Dawud Walid, Chief director of CAIR's Michigan chapter, said: "This ... should be condemned by all Americans who value human life and international law."

[57] In response, Walberg denied advocating the use of nuclear weapons, claiming that he merely "used a metaphor to convey the need for both Israel and Ukraine to win their wars as swiftly as possible" despite his reference to the US dropping atomic bombs on two Japanese cities to bring an end to WWII.