Chuck Schumer's name, he once proudly told a Jewish radio programme, comes from the word "shomer", or "guardian", and was given to the family by God in recognition of the fact that his ancestors guarded the Chortkov ghetto wall.

If Hillary Clinton makes it to the White House next January, the New York Senator looks set to become her most powerful ally in Washington and the shomer of her legislative agenda on Capitol Hill.

Current polls suggest that, albeit narrowly, the Democrats should pick up the four extra seats they need to win back control of the Senate and elect Mr Schumer as Majority Leader. With no Jew ever having been elected President or Speaker of the House of Representatives, that will make Mr Schumer the most powerful Jewish politician in US history.

Given that the Democrats have much less chance of wresting the House of Representatives from the Republicans, Mr Schumer's ability to marshal famously independent-minded senators behind Mrs Clinton will be key to her success. Even a legendary deal-maker such as Mr Schumer will have his work cut out with a wafer-thin majority and inevitable tensions within the Democratic caucus between liberals and their more conservative colleagues.

But the partnership between Mrs Clinton and Mr Schumer will be built on solid foundations. The two worked closely together for eight years as senators from New York. Unsurprisingly, there were tensions. Having served in the House of Representatives for 20 years, Mr Schumer was elected to the Senate in 1998. Barely two years later, however, the senator - who has a near-insatiable love of the limelight - found himself having to share the New York political stage with the former first lady. Nonetheless, their shared pragmatism, the need to work closely together in the wake of 9/11 and an implicit agreement that each would avoid trampling on the policy areas the other was passionate about helped to keep frictions at bay. Key, too, was Mr Schumer's dogged loyalty - a virtue Mrs Clinton and her husband prize above all others - during her failed 2008 presidential bid.

Politically, both are centrists and, on foreign policy, where the Senate has a key role, Mrs Clinton and Mr Schumer's views are likely to be aligned. Both are strong supporters of Israel with hawkish instincts, Mr Schumer breaking with President Barack Obama to oppose the Iran nuclear deal.

Mr Schumer is one of six Jewish Democrats running for Senate seats in November. Like Connecticut's Richard Blumenthal, Brian Schatz from Hawaii and Oregon Senator Ron Wyden, the New Yorker is heading for a comfortable re-election. Colorado's Michael Bennet has a comfortable poll lead, while Russ Feingold, the maverick former Wisconsin senator, is well ahead in his bid to regain the seat he lost six years ago. With Barbara Boxer retiring after 24 years representing California, a win by Mr Feingold will maintain the current number of Jewish senators at 10.