How did the Republican Party 'help Johnson achieve the kind of victory he desired' in the 1964 presidential election?

Lyndon Johnson was elected as the youngest minority leader in Senate. Soon after election the democrats had won majority leader in the senate. This gained Johnson huge skill which he later obtained passage of a number of key Eisenhower measures. Later in the 1960 campaign, Kennedy was Johnson running mate, Kennedy ended up winning and Johnson made the Vice President. After Kennedy died Johnson was sworn in as president. In 1964 Johnson won presidency with over 15,000,000 votes. The republican party was a ruling group of the time in the nation and though Kennedy wanted to stop civil rights, he never got time to. So the republicans in the nation all swarmed to Johnson to a new civil rights bill and tax cuts.

source: whitehouse.gov