help！big orange Big orange and white buttons reading

please tell me the meaning of this sentence“Big orange and white buttons reading 'Free the 99th Congress' have sprouted on the lapels all over Capitol Hill” from the text

Congress approved another emergency funding bill to keep the government operating another day, while lawmakers continued debate on an overall spending package for the year. NPR's Cokie Roberts reports. "Big orange and white buttons reading 'Free the 99th Congress' have sprouted on the lapels all over Capitol Hill. Members of Congress, ready to hit the campaign trail, just don't seem able to get out of Washington. The big five hundred and seventy-six billion dollar spending bill needed to keep the government functioning through this fiscal year is being debated on the Senate floor. The House passed the measure last night. But the other must-pass piece of legislation, the measure to allow the government to keep borrowing in order to pay its bills, is now not expected before tomorrow. Two other big bills still need one house to act on them. The House passed immigration reform yesterday. The Senate will deal with it tomorrow. The Senate passed a drug bill yesterday and now it looks like it will be tomorrow before that measure reaches the House floor. I'm Cokie Roberts at the Capitol.
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A 'button' in this context is a badge; 'orange and white' is the colour of these badges; the message written on them is what they 'read'. When things 'spring up' they suddenly appear, like flowering bulbs that suddenly appear in the Spring. They have 'sprouted' - like flowering bulbs, but not through the grass (on people's lapels instead).

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