He supported the Nixon administration's Vietnam policies, but broke with Republicans on the issue of birth control, which he supported. He also voted for the Civil Rights Act of 1968, although it was generally unpopular in his district.[61][62] In 1968, Bush joined several other Republicans in issuing the party's Response to the State of the Union address; Bush's part of the address focused on a call for fiscal responsibility.[63]
Though most other Texas Republicans supported Ronald Reagan in the 1968 Republican Party presidential primaries, Bush endorsed Richard Nixon, who went on to win the party's nomination. Nixon considered selecting Bush as his running mate in the 1968 presidential election, but he ultimately chose Spiro Agnew instead. Bush won re-election to the House unopposed, while Nixon defeated Hubert Humphrey in the presidential election.[64] In 1970, with President Nixon's support, Bush gave up his seat in the House to run for the Senate against Yarborough. Bush easily won the Republican primary, but Yarborough was defeated by the more conservative Lloyd Bentsen in the Democratic primary.[65] Ultimately, Bentsen defeated Bush, taking 53.5 percent of the vote.