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If she enters the contest, she will be the front-runner. Some eccentrics may not relish thinking about an election that is still 30 months away, but Mrs Clinton's shadow presidential campaign is already creaking into motion.
Big-name Democrats and former Obama campaign gurus are rallying to Ready for Hillary, a ginger group set up by Clinton-fans.
On May 2nd Senator Tim Kaine of Virginia gave a pre-emptive endorsement, praising Mrs Clinton's "deep history" in domestic policy and "unmatched" global contacts, and declaring it time for a woman president. Mr Kaine has form. As Virginia's governor he was one of Barack Obama's first declared supporters, startling those who had assumed that the 2008 presidential primary would be a coronation march for Mrs Clinton.
On May 3rd, at a dinner for the White House press corps, it was Mr Obama's turn. The president cracked gags about Mrs Clinton as his successor - Fox News would find it harder to convince Americans that "Hillary was born in Kenya", he joked - and his audience of insiders chortled knowingly. Opinion polls give Mrs Clinton hefty leads against hypothetical Republican challengers - a recent poll put her 12 points ahead of Jeb Bush, the former Florida governor, with still-larger margins of victory among women, the young and non-whites.
Many Democrats are keen to elect a woman president, especially one with Mrs Clinton's hard-earned experience. This desire is tinged, for some, with buyers' remorse after falling so hard for Mr Obama and his promise of a new, post-partisan politics. Such regret prompts a second reason to back Mrs Clinton: a sense that this is her turn. And the party's bench of alternatives is alarmingly thin. Joe Biden? Martin O'Malley?
The Washington wisdom is that Mrs Clinton, who will turn 69 a few days before the next presidential election, will not reveal her plans before congressional elections in November. She is said not to relish the prospect of another campaign. Lofted above domestic politics as secretary of state, her approval ratings soared. She dealt with foreigners, who do not have to be grovelled to, rather than voters, who do. Out of office, she has spent her time on charity work, lucrative speeches, receiving prizes and writing a new memoir, to be launched in June. If she runs, she will have to plunge straight back into the mire. The press, which she loathes, will go wild. (Vanity Fair is running a big Monica Lewinsky piece this week.)
Republicans are ready for Hillary, too. Some will remind older voters of scandals like Whitewater (involving real estate in Arkansas). But many voters have either forgotten, don't care or were born after it happened. (Plenty remember Bill Clinton as a sort of roguish uncle who presided over an economic boom.) So Republican leaders in the House of Representatives are digging for fresh dirt, preparing a select committee to probe the 2012 killing by terrorists of America's ambassador to Libya and three colleagues in Benghazi, near the end of Mrs Clinton's time at State. It will be Congress's eighth Benghazi investigation. Previous probes have faulted the government for failing to provide its envoys with adequate security. They have unearthed e-mails suggesting that officials initially sought to downplay the attack's broader significance for Mr Obama's Libya policies. Yet despite hours of hearings, Republicans have never found the scandal they crave: evidence that American troops or spies could have saved their colleagues in Benghazi but were told to stand down for reasons of timidity, political calculation or worse (listen to talk radio, and Mr Obama and Mrs Clinton should face treason charges). Still, in Washington, the select committee is seen as a backhanded compliment to Mrs Clinton's importance: it allows Republicans to torment her until 2016 if needs be.
Mrs Clinton is in a strong position. For all that, Democrats should not be too cocky. Their heroine might not run. Two big reasons for Democrats to back her - namely that the party owes her, and her rivals are either little-known or too left-wing to seek national office (hello, Senator Elizabeth Warren) - are of no interest to regular voters. Nationwide polls putting Mrs Clinton ahead of possible Republican rivals mean only so much at this stage. Mr Obama's genius in 2008 and 2012 was to mobilise groups who vote only sporadically, such as unmarried women, the young and non-whites. That required campaign wizardry. Mrs Clinton can buy that. But it also involved excitement. For all her virtues, Mrs Clinton does not make crowds swoon. Inspiring people to go out and vote will be her biggest challenge.
Stirring up apathetic voters
A veteran of previous Democratic presidential campaigns offers a cautionary tale. In 2008 Mr Obama lost Tennessee by a landslide. It is an increasingly conservative state, and he hardly campaigned there. But excitement landed Mr Obama a colossal win in two counties, built (to simplify) on black votes in Memphis and Nashville, and votes from leftish whites in Nashville. Now, says the veteran, go back eight years to Al Gore's lacklustre presidential campaign, which saw the Democrat lose Tennessee, his home state (though Bill Clinton had twice won it). If Mr Gore had turned out the same share of voting-age citizens as Mr Obama in just those two counties round Memphis and Nashville, he would have won Tennessee - and with it the White House.
Mrs Clinton's admirers grasp the importance of mobilisation. Ready for Hillary has Latino, black, women, young, Asian and gay subgroups. Allies recently founded a separate outfit, Faith Voters for Hillary. Fans talk of showing Mrs Clinton that if she decides to run, she will have a "grassroots army" behind her. Mrs Clinton cannot wait much longer to take the hardest decision of her career. Nobody wins the presidency by default.
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