WASHINGTON – Sen. Bob Corker’s announcement that he won’t seek re-election next year has left many Tennesseans wondering if the state’s senior senator, Lamar Alexander, will also call it quits when his current term expires in three years.

Alexander, a three-term senator and former governor, says he hasn’t decided if he’ll run again in 2020.

“I’m doing the things one would normally do to prepare to run for re-election,” the Maryville Republican said last week. “But one of the luxuries of a six-year term is I don’t have to think about such things every few years. What I’m focused on is doing my job, and right now that means making sure 350,000 Tennesseans who buy insurance in the individual market have insurance they can buy at an affordable price.”

If he does run for a fourth term, Alexander will do so in a political environment that is dramatically different than the one in which he ran his first race more than 40 years ago.

The Tennessee Republican Party has undergone tremendous growth and influence, campaigns in the state have gotten much more expensive, and, Alexander said, political discourse in general has grown a lot coarser than it was four decades ago.

“Forty years ago, in 1978, I walked a thousand miles across the state and tried to shake a thousand hands a day,” Alexander said, referring to his successful campaign for governor that year. “I don’t think I had two rude words said to me the whole time over six months. I doubt I could do that today.”

The amount of money that routinely flows into Tennessee’s high-profile political campaigns has increased ten-fold since then.

“I spent $2 million to win the governor’s race in 1978, 40 years ago, and I thought that was a lot,” Alexander said.

Corker spent close to $20 million in 2006, when he was first elected to the Senate in what has been the state’s most expensive political race. Candidates in next year’s race for governor also could spend a combined total of more than $20 million.

More:Sen. Bob Corker will not seek re-election next year

The political parties have changed, too, as conservatives in Middle and West Tennessee, following a national trend, have switched alliances from the Democrats to the Republicans and new GOP voters have moved into the state from places like Ohio, Michigan and other parts of the Midwest.

The result: Republican primaries are bigger – and more competitive.

When Winfield Dunn was elected governor in 1970, nearly 245,000 people voted in the Republican gubernatorial primary. Almost three times that many, or 651,000, voted in the GOP primary in 2014, when Republican Bill Haslam won his second term.

In 1966, when Republican Howard Baker Jr. was elected to the U.S. Senate, about 150,000 people voted in the GOP primary, while 750,000 voted in the Democratic primary. In 2012, when Corker won his second term, the numbers were dramatically reversed, with 457,000 people voting in Republican primary and 161,000 voting in the Democratic primary.

“When I first began running in the '70s, the conservatives who I appealed to were in the general election,” Alexander said. “Now, they are in the Republican primary.”

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Alexander has won all six of the Republican primaries in which he has run and five of the six general elections in which his name has appeared on the ballot. His only loss was in 1974, when he won the GOP nomination for governor in the primary but lost in the general election to Democrat Ray Blanton.

Since then, “I’ve had to adjust quite a bit to a changing electorate because different people are voting in the primaries,” Alexander said. "I’ve adjusted well enough to win. But those are some pretty big changes.”