Amash received national attention when he became the first Republican congressman to call for the impeachment of Donald Trump, a position he maintained after leaving the party.

Amash formed an exploratory committee to seek the Libertarian Party presidential nomination in the 2020 election, before announcing in May of that year that he would not run for president.

[18] Glenn Steil Sr., the incumbent state representative for Michigan's 72nd House District, was unable to run for reelection in the 2008 election due to term limits.

[27] During the campaign he advocated politics supported by the Tea Party movement and defeated Democratic nominee Patrick Miles Jr. in the general election.

[28][29][30] He joined Representatives Tim Huelskamp and David Schweikert in a letter to Speaker of the House John Boehner, demanding to know why they had lost their committee positions.

[60][61] On May 16, he withdrew his name from consideration for the Libertarian nomination, citing increased political polarization and economic effects of the COVID-19 pandemic that would make campaigning difficult.

[68] In November 2022, Amash tweeted that he would be willing to serve as a "nonpartisan" Speaker of the United States House of Representatives, receiving support from Colorado Governor Jared Polis.

[71][72][73] In an interview with Reason, he said he would "Open up the process" for creating and passing legislation and criticized Speaker candidate Kevin McCarthy as someone who "cares only about power" rather than policy.

[78][79][80] Amash was regarded as one of the most libertarian members of Congress, receiving high scores from right-leaning interest groups such as the Club for Growth, Heritage Action, and Americans for Prosperity, and praise from limited-government think tanks and nonprofit organizations.

[94][98] In May 2012, Amash was one of seven Republicans to vote against the Prenatal Non-Discrimination Act, which would have made it a crime for a doctor to perform an abortion on a woman who wants to end a pregnancy based on the gender of the fetus.

[107][108] In 2015, Amash and Representative Ted Lieu (D–CA) introduced a bill[109] to block the Drug Enforcement Administration (DEA) from financing its Cannabis Eradication Program through civil asset forfeiture.

[114][115] In March 2010, Amash was the only member of the Michigan House of Representatives to vote against making benzylpiperazine a schedule I drug, saying that penalties for nonviolent crimes shouldn't be increased.

[130] Amash initially opposed the American Health Care Act, describing it as "Swampcare",[131] tweeting that "It didn't take long for the swamp to drain @realDonaldTrump"[132] and criticizing House leadership for attempting to "ram it through.

[135] Amash notes that campaign finance poses significant challenges, but states, "I don’t know how to resolve it because I’m a big believer in free speech.

[143] On June 12, 2013, he called for Director of National Intelligence James Clapper to resign for stating at a Senate committee hearing in March that the NSA did not collect data.

[145][146][147] In 2016, Amash was one of three Republicans to vote in favor of an amendment to close Guantánamo Bay and potentially allow federal officials to transfer detainees to facilities in the United States.

[148] Amash opposed President Donald Trump's 2017 executive order to ban citizens of seven majority-Muslim countries from entering the United States.

[150] The Amash amendment would have required the government in criminal cases to seek a warrant based on probable cause before searching surveillance data for information about Americans.

[157][158] He supported the result of Obergefell v. Hodges (in which the Supreme Court held that same-sex couples cannot be deprived of the fundamental right to marry) on the grounds that government-issued marriage licenses should not be "necessary to validate the intimate relationships of consenting adults.

"[159][160] In 2015, Amash was among 60 Republicans voting to uphold President Barack Obama's 2014 executive order banning federal contractors from making hiring decisions that discriminate based on sexual orientation or gender identity.

He said, "Those who serve in our Armed Forces deserve the best medical care...With respect to transgender persons, we should focus on the best science, not the political or philosophical opinions of partisans.

"[174] In February 2019, Amash was the only House Republican to co-sponsor a resolution to block Trump's declaration of a national emergency to redirect funds to build a wall on the U.S.-Mexico border without a congressional appropriation for such a project.

In July 2011, he sponsored an amendment to the Department of Defense Appropriations Act that would have prevented funding for operations against Gaddafi's government and Amash later stated that President Obama's actions during the Libyan Civil War were unconstitutional without authorization from Congress.

[184] On March 14, 2016, Amash joined the unanimous vote in the House to approve a resolution declaring the Islamic State of Iraq and the Levant (ISIL) to be committing genocide against religious minorities in the Middle East (it passed 383–0), but joined Representatives Tulsi Gabbard (D-HI) and Thomas Massie (R-KY) in voting against a separate measure creating an international tribunal to try those accused of participating in the alleged atrocities (it passed 392–3).

[190] In 2019, Amash signed a letter led by Representative Ro Khanna and Senator Rand Paul to Trump arguing that it is "long past time to rein in the use of force that goes beyond congressional authorization" and that they hoped this would "serve as a model for ending hostilities in the future – in particular, as you and your administration seek a political solution to our involvement in Afghanistan.

Amash felt that Lewis' comments were "inappropriate" but said that Trump's response should have been "dignified and conciliatory to the extent possible" instead of "personal jabs, attacking his district".

[204] In April 2017, Dan Scavino, a senior Trump White House aide, called for Amash to be defeated in a Republican primary challenge.

"[201][205] In May 2017, Trump was accused of pressuring fired FBI director James Comey to end an investigation into former national security adviser Michael Flynn.

[213] Amash also said that Attorney General William Barr "deliberately misrepresented" the report's findings[214] and that partisanship was making it difficult to maintain checks and balances in the American political system.

"[81] House Minority Leader Kevin McCarthy, a Republican, claimed that Amash "votes more with Nancy Pelosi than he ever does with me"; PolitiFact evaluated this as false.