I can't run this cause I don't have the libraries, but just looking at it codewise. You could re-run setup() like any other function, but you probably don't want to do this. Instead just run the feeder function that you need to refresh with the spacebar. See the code below (untested, but should work the same as your old code, I only re-arranged it to a seperate function ).

1. import net.obxlabs.romefeeder.*; //romefeeder
2. import com.sun.syndication.feed.synd.*; //ROME
3. import processing.serial.*;
4. Serial myPort;
5. TwitterFeeder feeder;  // the feeder
6. boolean loaded = false; // flag that indicates if the search is loaded
7. int feedRate = 7*1000; // rate for displaying posts (in miliseconds)
8. int feedLast = 0;  // time of the last displayed post
9. SyndEntry entry; // feed entry
10. TwitterFeeder feeder2;  // the feeder
11. SyndEntry entry2; // feed entry
12. PFont font; // the font
13. static final int WORD_FONTSIZE = 128;  //self size
14. static final int TEXT_FONTSIZE = 24;   //rest of text size
15. static final int TEXT_WIDTH = 400;      //text width (in characters)
16. int chooser;
17. String textmark;
18. String a ;
19. //search query
20. String QUERY = "protestors";
21. String QUERY2 = "Gadhafi";
22. String topString = ""; //string of text that appears before 'self' in the tweet
23. String bottomString = ""; //string of text that appears after 'self' in the tweet
24. 
    
25. void setup() {
26.   //arduino connection///////////////////////////////////////////////////////////////////////////////////
27.   println(Serial.list());
28.   myPort = new Serial(this, Serial.list()[1], 9600);
29.   myPort.buffer(1);
30.   ///////////////////////////////////////////////////////////////////////////////////////////////////////
31.  
32.   size(600, 300);
33.   frameRate(30);
34.   smooth();
35.  
36.   //create and set the font
37.   font = createFont("bluehigh.ttf", 12, true);
38.   //add a loading prompt
39.   textFont(font, 24);
40.   text("Loading Tweets...", width/2, height/2);
41.   feeder();
42. }
43. 
    
44. void feeder() {
45.   //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
46.   ///FEEDER CREATIONS
47.   //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
48.   //create the feeder
49.   feeder = new TwitterFeeder();
50.   feeder.verbose = true;
51.   feeder.sort(Feeder.PUBLISHED_DATE);
52.   feeder.setLoadFeedCallback(
53.       new FeedCallback() { public void event(SyndFeed feed) { postLoadFeed(feed); } }
54.   );
55.   feeder.search(QUERY);
56.   feeder.setUpdateInterval(7*1000); // milliseconds
57.   feeder.startUpdate();
58.  
59.     //create the feeder2
60.   feeder2 = new TwitterFeeder();
61.   feeder2.verbose = true;
62.   feeder2.sort(Feeder.PUBLISHED_DATE);
63.   feeder2.setLoadFeedCallback(
64.       new FeedCallback() { public void event(SyndFeed feed) { postLoadFeed(feed); } }
65.   );
66.   feeder2.search(QUERY2);
67.   feeder2.setUpdateInterval(7*1000); // milliseconds
68.   feeder2.startUpdate();
69.  
70.   //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
71.   ///END FEEDER CREATIONS
72.   //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
73.   println("feeder 1 and 2 loaded");
74. }
75. 
    
76. //flag when the search is done loading
77. void postLoadFeed(SyndFeed feed) {
78.   //flag as loaded
79.   loaded = true;
80. }
81. 
    
82. void draw() {
83.   //if the search is not done loading then wait
84.   if (!loaded) return;
85. //  String a = names[int(random(names.length))];
86. //  println(a);
87.  
88.   chooser= int(random(0,2));
89. //  println(chooser);
90.  
91.   switch(chooser){
92.  
93.  
94.   case 0:
95.  
96.  
97.  
98.   if ((feeder.hasNext()) && (millis()-feedLast >= feedRate)) {
99.     //get the next entry
100.     entry = feeder.next();
101.    
102.     //parse the entry title as text
103.     parseEntry(entry.getTitle(),QUERY);
104.    
105.     //update the feed timer
106.     feedLast = millis();
107.    
108.     myPort.write(0);
109.    
110.  background(0);
111.    //draw the rest of the tweet
112.   textFont(font, TEXT_FONTSIZE);
113.   fill(255);
114.   stroke(0);
115.   textAlign(LEFT, BOTTOM);
116.   text(topString, 205, -85, 350, 200);
117.   textAlign(RIGHT, TOP);
118.   text(bottomString, 50, height/2 + 54, 350, 190);
119.  
120.   //draw the searched text
121.   fill(255);
122.   stroke(0);
123.   textFont(font, WORD_FONTSIZE);
124.   textAlign(CENTER, CENTER);
125.   text(QUERY.toUpperCase(), width/2, height/2);
126.    
127.     break;
128.   }
129.   
130.    case 1:
131.   
132.     if ((feeder2.hasNext()) && (millis()-feedLast >= feedRate)) {
133.     //get the next entry
134.     entry2 = feeder2.next();
135.    
136.     //parse the entry title as text
137.     parseEntry(entry2.getTitle(),QUERY2);
138.    
139.     //update the feed timer
140.     feedLast = millis();
141.    
142.     myPort.write(1);
143.    
144. background(0);
145.   //draw the rest of the tweet
146.   textFont(font, TEXT_FONTSIZE);
147.   fill(255);
148.   stroke(0);
149.   textAlign(LEFT, BOTTOM);
150.   text(topString, 205, -85, 350, 200);
151.   textAlign(RIGHT, TOP);
152.   text(bottomString, 50, height/2 + 54, 350, 190);
153.      
154.   //draw the searched text
155.   fill(255);
156.   stroke(0);
157.   textFont(font, WORD_FONTSIZE);
158.   textAlign(CENTER, CENTER);
159.   text(QUERY2.toUpperCase(), width/2, height/2);
160.   
161.     break;
162.   }
163. }
164. }
165. //parses the tweet and stores the to strings
166. //that are displayed above and below the word 'self'.
167. void parseEntry(String title, String question) {
168.   //make sure the magic word is there.
169.   if (title.toLowerCase().indexOf(question) == -1) return;
170.  
171.   //get the strings before and after the magic word
172.   topString = title.substring(0, title.toLowerCase().indexOf(question));
173.   bottomString = title.substring(title.toLowerCase().indexOf(question) + question.length());
174.   //clean up
175.   topString = topString.trim();
176.   bottomString = bottomString.trim();
177. }
178. 
     
179. void keyPressed() {
180.   if (key == ' ') {
181.     feeder();
182.   }
183. }