In 1961, he introduced the bill to create the Indiana Port Authority to oversee the creation of seaports along Lake Michigan.

On March 1, 1968, he announced his intention to run for the Republican nomination for Indiana's Second Congressional District to succeed Charles A. Halleck who was retiring.

In 1970, Albert Harrigan, who was a candidate in the 1968 primary, and Donald W. Blue, the mayor of Lafayette, announced that they would challenge Landgrebe for the Republican nomination.

[24] He received his largest amount of support throughout his House career in the 1970 primary with 56.48% of the vote with the rest being divided between Harrigan and Blue.

The Democratic Party fared well nationally during the 1970 House elections and Landgrebe narrowly held onto his seat, by only 1,204 votes against Phillip Sprague.

In the general election, he easily defeated Purdue University professor Floyd Fithian by riding off the coattails of Richard Nixon's landslide victory in the 1972 presidential election and in Indiana, where Nixon received 66.11% of the vote statewide against George McGovern and received 76,000 more votes than Landgrebe in the second congressional district.

[33][34] In 1972, Landgrebe was arrested during an official visit to the Soviet Union to observe their education facilities, due to him distributing Bibles, which he did as he was a devout Lutheran.

[35] In 1973, he became ill and was treated at Walter Reed National Military Medical Center for ten days, during which Nixon visited him.

[38] When asked about the damning tape transcript and the resultant rapid collapse of support for the president among Republicans in Congress and the likelihood that Nixon would be impeached, he said: "Don't confuse me with the facts.

[41] Landgrebe was named as one of the top "Ten Dumbest Congressmen" by New Times alongside Senators William L. Scott and Roman Hruska and Representatives William A. Barrett, Harold Donohue, Floyd Spence, Harold L. Runnels, John Rarick, and Joseph J.

[42] Landgrebe received a massive backlash from voters in his district for his support of Nixon and was resoundingly defeated in the 1974 election, although this was the only time in his House career that he did not face a primary challenge.

[46] In 2019, Jake Tapper compared Senator Lindsey Graham to Landgrebe over his position on Trump's actions in Ukraine and the Congressional impeachment inquiry into it.

In the past he would personally deliver through the picket line such as in 1961 when as a state senator he made a delivery to a pool company plant that was experiencing a strike.

[48] The former congressman personally confronted picketers with a tractor trailer this time as well and on February 13, he completed two trips into the Union Rolls plant to pick up and haul away merchandise.

[51] When the USS Pueblo was captured by North Korea in 1968 he supported sending a forty eight hour ultimatum that would threaten nuclear warfare unless all of the Americans were returned.

[52] In 1972 the House of Representatives voted to approve the Strategic Arms Limitation Talks treaty between the United States and the Soviet Union that had a "freeze" on offensive missiles for five years.

He supported the "Dangerous Substances Bill" which gave drug dealers sentences from five years to life imprisonment and a mandatory fine of $50,000.