The Wisconsin Republican has built a congressional career as the Republican Party's budget savant, but Ryan is perhaps in his career's most difficult bind as he tries to engineer passage of an alternative to President Barack Obama's $4.1 trillion budget that he sent to Congress on Tuesday. Republican defense hawks combined with Democrats seeking relief from a squeeze on domestic programs to power the increases forward, and it was Boehner's final major accomplishment as he cleared away unfinished business for Ryan. So-called mandatory spending such as Social Security, Medicare and health care costs under the Affordable Care Act is responsible for the rest of the $4 trillion-plus federal budget. [...] the upcoming GOP budget — which would give the House and Senate Appropriations committees the money to do their work — must pass with nearly unanimous Republican support since it will also call for big, albeit nonbinding, cuts to domestic programs favored by Democrats. Many tea party Republicans, including the 40 or so members of the hard-right Freedom Caucus that engineered Boehner's resignation and blocked Majority leader Kevin McCarthy, R-Calif., from succeeding him, say they can't go along with any GOP budget that endorses last year's deal.