In 1964, Congress overcame a 57 day filibuster to pass the civil rights act of 1964.
When Nixon won the presidency in 1968 over Hubert Humphrey and George Wallace, his party gained a healthy 5 seats in the senate but just a meager 5 seats in the House. Democrats were still firmly in control and would end up retaining both houses of congress throughout Nixon's entire presidency. Thus congressional Democrats would play a substantial role in setting the policy and agenda during the the Nixon Administration.
Nixon himself had campaigned as a centrist in his party, wanting to be in between the conservative Barry Goldwater wing and the more liberal Nelson Rockefeller wing of his party.Politics was much less cut and dry as it is today. There were a substantial amount of liberals and conservatives in both parties. Democrats owed much of their majorities to a coalition of liberals in the east/west and conservatives in the south.
Just as Nixon was entering his presidency, he faced the issue of extending the Voting Rights act of 1964. Some of the key provisions (pre-clearance and the automatic trigger) were set to expire. Most civil rights activists just wanted congress to simply renew the measures. But Southerners on the other hand, felt they had made adequate progress in registering black voters and felt they no longer needed pre-clearance or an automatic trigger. Some even went so far to declare that the provisions of the VRA act such as a ban on literacy tests, should extend nationwide rather than focus primarily on only southern states. With that said, the civil rights law still had strong support of many Republicans like the honorable William McCulloch of Ohio and incoming senate minority leader, Hugh Scott of Pennsylvania.
Nixon had championed a southern strategy to win the presidency and employed South Carolina Senator Strom Thurmond as his key adviser on Southern policy. Nixon wanted to prove himself to many of the southern conservatives he had won over and thus was quite eager to push for a nationwide ban on literacy tests. He agreed with many of his southern conservative colleagues and a pushed for a bill that would include no pre-clearance or automatic triggers. In addition his bill would move voting rights cases from the more liberal leaning DC court to local federal courts and create a federal commission to investigate voter fraud & discrimination.
After heavy lobbying from the white house the bill narrowly passed the house 213-209. The GOP voted 132-52 in favor while Democrats voted 81-157 against. You can view the entire vote break down here. This vote was more regional than it was partisan. Non Southern Democrats overwhelming voted against the bill and were joined by many northern Republicans. For example, the Massachusetts house delegation voted entirely in opposition while the Alabama delegation voted in unison for the bill. Even the Democratic leadership line was divided. Tip O'Neill, Carl Albert, John McFall, and Tom Foley all voted against while Jim Wright and Hale Boggs voted in favor of the bill. Both David Obey (D-WI) and John Conyers (D-MI) ,the current dean of the house, voted against the bill.
But the senate was another story, as moderate/liberal Republicans made up a healthy amount of the chamber. These Republicans were quick to join with liberal Democrats to undo all these substantial changes. Instead the chamber voted 70-18 to extend the VRA with new provisions such as lowering the voting age to 18 add an additional trigger mechanism that brought parts of several non-southern states under federal supervision. Roman Hruska , the conservative senator of Nebraska, was the only non-southern senator to vote against the bill.
The Senate bill returned to the house where it passed by a key procedural vote of 224-183. Democrats supported the bill 165-66 and the GOP split 59-117 against. This time the Democratic leadership was fully united behind the bill.
With it now apparent the bill would pass in the house, several more Democrats and Republicans switched over to support the bill (including minority leader Ford). Even some southern Democrats came around to supporting the bill believing they could benefit from higher turnout from black voters. The final tally in the house was 276-136 (Democrats 174-58 in favor and GOP 102-78 in favor)
When the bill reached Nixon's Desk
The president grumbled that there was no political windfall for the GOP because young people and blacks voted Democratic, but he agreed to sign the bill because he felt "an obligation not to have the god damn country blow up." His fears applied more to blacks than to young people. If the measure had simply been an extension of the franchise to 18 year-olds, Nixon told his aides, he would have vetoed it.
Conservatives were less than thrilled by the turn of events. The provision regarding a lower voting age of 18 was later struck down by the courts and restricted 18 year-olds to voting in only federal elections. Congress would later ratify the 26th Amendment to remedy the situation.