An opponent ran ads focusing on Bost's anger, but many voters, according to NPR, "see his fury as well-placed.

[19] Illinois's largely agricultural 12th district was historically Democratic-leaning, but had been trending Republican, with President Obama having carried it by only 2 percentage points in 2012.

[12] The Cook Political Report rated the race a "Toss Up" and the National Journal ranked the district the 21st most likely to flip Republican in 2014.

[24] Bost won the election with 53% of the vote to Enyart's 42%, with Green Party candidate Paula Bradshaw taking 6%.

After being elected to the House, Bost said he did not plan to acquire a second residence, but would sleep in his office while in Washington.

In its endorsement, the union cited Bost's, "strong record in support of public education in the Metro East and Southern Illinois.

[35] In November 2014, Bost described President Obama, his former colleague in the Illinois legislature, as a "fluke" and said that "nobody ever thought he was going to rise."

He recalled a time when Obama, speaking to a group of reporters as Bost walked by, had said to them: "There you have it, one of the rich Republicans."

[13] After James Hodgkinson shot at GOP congressmen who were playing baseball in Virginia on June 14, 2017, injuring Steve Scalise, Bost said that his office had previously received phone calls from the attacker.

[40][41] In April 2016, a Bost bill to change how the government defines farms and ranches as small businesses passed the House with bipartisan support.

[42] At a March 2017 "telephone town hall," Bost spoke about health care with several constituents who criticized Obamacare.

[44] Bost voted for the Tax Cuts and Jobs Act of 2017,[45] saying he believed the bill would enable businesses to compete globally and thereby improve the economy.

[46] In December 2017, Bost signed a letter requesting that two education-related portions of the Internal Revenue code, one providing tuition breaks and the other incentivizing employees "to accept tax-free educational assistance from employers," be left unchanged in the new tax bill.

[48] In December 2020, Bost 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[49] 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.

[50][51][52] In 2015, Bost condemned the Supreme Court ruling in Obergefell v. Hodges, which held that same-sex marriage bans violated the constitution.

[55] Bost was among the 71 Republicans who voted against final passage of the Fiscal Responsibility Act of 2023 in the House.

[57][58] In 2024, Bost voted against the $60 billion military aid package for Ukraine, although much of the money would go to his constituency.

He has said that his political hero is John Alexander Logan, an Illinois Democrat who had switched parties when the Civil War began.

He was arrested and charged with criminal damage to property and reckless misconduct in relation to the incident, but was acquitted at trial.

[86] In 2006, authorities confronted Bost after he failed to report that his gun was stolen after it was used to threaten another man's life.