March 25 (Bloomberg) — Last week, when Hillary Clinton released a video announcing her support for gay marriage, Twitter went wild.

It was totally expected — her husband and daughter took the same position months earlier — and didn’t have as much political import as Ohio Republican senator Rob Portman’s announcement this month that he now favors same-sex marriage.

The rules are different for Hillary Clinton. No non-incumbent in the history of contemporary U.S. presidential politics ever looked so formidable three years before an election.

Ask almost any Democrat and the automatic assumption is that Clinton will be the party’s 2016 nominee; a top West Virginia Democrat predicts she would carry that state, which President Barack Obama lost 62 percent to 35 percent in 2012. Ask most Republicans who has the best shot to be the 45th president, and they’ll acknowledge it is Clinton.

In conversations last week with more than a half dozen Clinton associates — people who know her very well politically or personally — there was a consensus: She’s more likely to run than not. The presidential bug hasn’t left her and she passionately wants to see a woman president. Still, her candidacy isn’t a foregone conclusion; those who say they know, don’t; and there are several pressing questions outstanding.

First is her health. She just went through a fairly serious illness in December that sidelined her for a month. She developed a blood clot, an ailment she had suffered at least once before. Doctors who stress they have no knowledge of her particular condition say a pattern of clots is worrisome.

She’ll turn 69 a week before the 2016 election — younger than Ronald Reagan in 1980 or John McCain in 2008, and questions about her age reflect sexism. But questions about whether she can still bring her extraordinary vibrancy to any political task don’t.

Then there’s the health of the country in a few years. If the economy continues to improve and the world is relatively stable, her credentials to succeed and expand on Obama’s record, to build a more prosperous middle class and enhance America’s global standing, will be potent.

If the world economy deteriorates and U.S. unemployment hits double digits again or if there’s a conflict in the Middle East or on the Korean Peninsula, all bets are off.

Over the past 60 years, only once, in 1988, has an incumbent party been given more than eight consecutive years in the White House.

Finally, what did she learn from the 2008 primary run? It was a disaster. She sought to inherit the nomination rather than capture it. She ran as a tough, hawkish, establishment candidate when most Democrats wanted an anti-war, anti-establishment nominee. Her campaign dissolved into chaos as she stubbornly refused to change. Ultimately, she dumped her campaign manager and the chief strategist of the flawed effort, but it was too late.

Would she pick better people next time and master the profound changes in political elections? She might start with Sasha Issenberg’s book, The Victory Lab, which describes the analytical revolution in U.S. politics. In 1991, there was a so-called “Carville primary,” as Democratic contenders vied for the services of the hottest political consultant, James Carville.

The equivalent this time might be the Teddy Goff primary, to earn the assistance of the digital wunderkind who directed social media for the Obama campaign.

Then, unlike in 2008, Clinton would have to adopt a strategy that fits the times. There is no need for her to rush. She’s selectively staying in touch with key players, is expected to write a book, settle into a role in a nonprofit focusing on global and domestic issues of prime concern, and get some rest.

One of the reasons Democrats are so eager for Clinton to run is that they have a weak bench. Vice President Joe Biden, popular within the party and a loyal and important Obama lieutenant, would be almost 74 on Election Day 2016. That’s four years older than Reagan was in 1980, when he was the oldest man ever elected president.

New York governor Andrew Cuomo incurs animosity with more than a few national Democrats and his controlling, secretive ways would be a challenge in a national campaign. Maryland governor Martin O’Malley, attractive and articulate, doesn’t seem ready for prime time.

Democrats have a long tradition of upending frontrunners by picking nominees such as George McGovern, Jimmy Carter and Obama. Hierarchical Republicans usually go with the establishment candidate. Thus the cliché that Republicans like to fall in line and Democrats like to fall in love.

With Clinton — who has rebounded from a defeat better than any recent presidential aspirant, including Reagan post-1976 — Democrats want to fall in line. Republicans are desperate to find a candidate to love.

There are more than 1,000 days before any votes are cast. Another cliché is more telling: That’s an eternity in politics.

(Albert R. Hunt is a Bloomberg View columnist. The opinions expressed are his own.)

AP Photo