TCPalm » Sen. Marco Rubio, R-Florida, Tuesday cast doubt on Brightline’s approval for $1.75 billion of tax-exempt bonds, crucial financing for the Miami-to-Orlando passenger railroad. Rubio’s letter to transportation Secretary Elaine Chao follows a Capitol Hill hearing last week during which congressmen blasted Brightline and the U.S. Department of Transportation — which approved the bonds — for possibly circumventing federal law and defying congressional intent regarding the financing.