This system was needlessly confusing and arcane, and made comparison of tax rates from one jurisdiction to another very difficult (which some stated was one of the prime reasons for its existence).

Having helped pass the call for the convention, Allen then set out to shape it to his ideas, firstly by winning election to it as a delegate while continuing to serve as assessor of property.

Allen soon became the leading figure of the convention, and its proposal, which called for an assessment of 25% of appraised value on residential and agricultural property and 40% on commercial property and even higher on utilities, was essentially Allen's plan, and was subsequently approved by Tennessee voters and remains the law as of 2012 except that the U.S. Senate overrode the higher tax rate on utilities at the urging of Senator Howard Baker.

In this race Allen was shocked to have finished fourth, well short of participation in the runoff (which again was won by Briley over runner-up Casey Jenkins, a former motion picture projectionist who had gained notoriety largely as an opponent of forced busing for school desegregation).

In 1975 when Richard Fulton was elected mayor to succeed Briley and resigned as Congressman, Allen entered the crowded Democratic primary field in the ensuing special election, and won, beating the incumbent district attorney Thomas Shriver, legislator Mike Murphy, and attorney (later federal Sixth Circuit judge) Gilbert Merritt, largely because of having far more name recognition than any other candidate and because of his populist attack on high rates being charged by local electric and gas utilities.

As the Republicans had by this time given up on making serious bids for a district they hadn't won since Reconstruction, his victory in the special general election was a foregone conclusion, and he took office on November 25, 1975.

His primary issue was the higher electricity rates being charged by the Tennessee Valley Authority, primarily in order to finance its ambitious nuclear energy program.

However, Allen was regarded by many as increasingly a relic of an earlier era; he tended to address all issues at discursive length in the tradition of Southern country lawyers.

In some circles in Washington, he was given the derisive nickname "The Tennessee Talking Horse", as an indication of his perceived verbosity (a title previously held by former Memphis Congressman Dan Kuykendall).

The only candidate who didn't withdraw from the race a few days earlier, State Senator Bill Boner, thus appeared alone on the Democratic primary ballot.

While one of the erstwhile opponents, Elliot Ozment, then tried to conduct a write-in campaign, this proved totally futile, and Boner won the nomination, and in effect, election in November.